Lower esophageal ring.
D004945:Esophagoscopy; D004947:Esophagus / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007413:Intestinal Mucosa / Q000473:pathology; D008297:Male; D008365:Manometry; D008875:Middle Aged; D011859:Radiography